1. Field of the Invention
The present invention relates to an absorption type cooling and heating apparatus for operating in three different modes: cooling operation, heat-pump heating operation, and direct-burner or direct flame heating operation, and particularly to an absorption type cooling and heating apparatus arranged in which a cooling operation and a heat-pump operation are carried out at optimum conditions and can readily be switched to a direct-burner heating operation.
2. Description of the Related Art
There has been increased the demand of an absorption type cooling and heating apparatus which can carry out a heat-pump heating operation with the use of heat pumped up by an absorber in addition to a cooling operation. Such a heat-pump heating may however be declined in the efficiency of pumping up an energy of heat as the ambient temperature drops down. For compensation, an improvement is disclosed in Japanese Patent Publication (Heisei) 6-97127 where if the ambient temperature is too low, the heat-pump heating operation is replaced with a direct-burner heating operation.
We, the applicants, have developed an absorption type cooling and heating apparatus which can easily switch between a cooling operation, a heat-pump heating operation, and a direct-burner heating operation as is disclosed in Japanese Patent Laid-open Publication (Heisei) 10-197008. Our reference cooling and heating apparatus has a closed circulation loop where, when heat-pump heating operation fails to generate a required power of heating, a refrigerant in vapor heated to a high temperature by a regenerator is transferred to a condenser where it comes into contact with a contact with a cooling water conduit and is thus condensed before returned back to the regenerator. This allows the refrigerant vapor extracted from the regenerator to be fully condensed by the condenser but not circulated from the condenser to an evaporator, thus shifting from the heat-pump heating operation to the direct-burner heating operation.
Also, we have developed another absorption type cooling and heating apparatus which has a dedicated circulation path for permitting the refrigerant to spontaneously drop down from a condenser to a rectifier thus to circulate from the condenser via the rectifier to a regenerator as disclosed in Japanese Patent Laid-open Publication (Heisei) 10-267448.
The absorption type cooling and heating apparatus with the dedicated circulation path however needs an extra conduit of the dedicated circulation path for circulating the refrigerant, hence increasing the number of joints. This is unfavorable for generating a degree of vacuum in the system of the apparatus. The apparatus may be modified with a bypass where the refrigerant over-flown from the condenser is directly returned back to the top portion of the rectifier. It is yet necessary for inhibiting overflow in the other operation mode than the direct-burner heating operation to save a more amount of the refrigerant in the condenser. As a result, the duration of time from the initiation of the direct-burner heating operation to the start of overflow will be extended thus creating substantially a time delay before starting the direct-burner heating operation. As the refrigerant remaining in the condenser stays out of the actual operation, the energy spent for saving the refrigerant prior to the overflow will be wasted.
Also, the refrigerant remains at a considerable amount in the condenser at the start-up and will not move into the evaporator before a substantial difference in the pressure is developed. Therefore, the solution circulated from the absorber to the regenerator becomes highly dense and its density may be too high in the regenerator. This results in a less-vapor state in the regenerator. It is hence needed for preparing an excess amount of the refrigerant in the evaporator at the start-up to feed a redundancy of the refrigerant into the evaporator.
It is an object of the present invention to provide an absorption type cooling and heating apparatus which carries out a cooling operation or a heat-pump heating operation at optimum conditions and when needed, readily switch the operation mode into a direct-burner heating operation while eliminating the foregoing drawbacks.
Present invention having the first feature comprising an evaporator for holding a refrigerant, an absorber for allowing an absorbent solution to absorb a refrigerant vapor generated in the evaporator, a regenerator for recovering the density of an absorbent in the absorbent solution by heating up to extract the refrigerant vapor from the absorbent solution, a refrigerant vapor passage for transferring the refrigerant vapor from the regenerator to a condenser, and the condenser for condensing the refrigerant vapor which is returned back to the evaporator, where in a cooling operation, a heat-pump heating operation, and a direct-burner heating operation can be performed selectively, said absorption type cooling and heating apparatus comprising, a first conduit for transferring the condensed refrigerant generated in the condenser to the evaporator, a second conduit for transferring the absorbent solution from the absorber to the regenerator, a branch conduit branched from the first conduit, and a switching device for selectively communicating the branch conduit to the second conduit.
According to the first feature of the present invention, the communication between the branch conduit and the second conduit by the action of the switching device allows the refrigerant to flow from the condenser via the branch conduit and the second conduit to the regenerator. When the branch conduit and the second conduit are disconnected from each, the refrigerant is transferred via the first conduit to the evaporator.
Present invention having the second feature in which the switching device is a first check valve for allowing the flow from the condenser via the branch conduit to the regenerator while a second check valve is also provided for allowing the flow from the absorber to the regenerator, the first and second check valve communicated with each other at the downstream side.
According to the second feature of the present invention, at the start-up mode or the direct-burner heating operation mode where the pressure is lower at the absorber side than at the condenser side, the second check valve is closed to inhibit the flow of the solution from the absorber to the regenerator. On the other hand, at the heat-pump heating operation mode where the pressure is higher at the absorber side than at the condenser side, the first check valve is closed to inhibit the flow of the refrigerant from the condenser to the regenerator.
Present invention having the third feature in which the first and second check valves are assembled in a single unit having a movable valve portion provided at the downstream junction thereof so that the valve portion can be shifted to each end of its movement by a pressure difference between two fluids introduced into the input ports of the first and second check valves, thus the first check valve is shut up when the valve portion shifted to one end of its movement and the second check valve when the valve portion shifted to the other end.
According to the third feature of the present invention, the first and second check valves are assembled together with the single valve provided for common use, hence contributing to the simplification of the overall arrangement. Also, the first and second check valves are selectively operated with the valve shifted for opening by the action of a pressure difference between two fluid inputs. As a result, no actuator will be needed for driving the valve.